I took the character sheet/drawing that I was given and printed it out to the exact proportions I needed it to be.Then I usually sit for a day and figure out how to assemble and disassemble the piece in my mind. I really try to visualize it, so I have an idea of what I'll be doing.After that, I roughly bulk out each piece (arms, torso, legs, etc) to make sure the proportions are right and then go from there.

It's a lot of trial and error, and eventually I cast certain pieces in resin so I don't mess up the original sculpted piece. It's very annoying but a great fun challenge at the same time